Skin moles tied to breast cancer risk: studies

NEW YORK (Reuters Health) - The number of moles a woman has
may be tied to her risk of developing breast cancer, according
to two new studies.

The studies don't prove that moles cause breast cancer or
that women with a lot of moles will definitely get breast
cancer. Instead, they suggest there may be a small genetic or
hormonal link between the two.

"This shouldn't be a concern for women with moles, because
we don't think the relationship is causal," said Marina
Kvaskoff, the lead author of one of the new studies.

Kvaskoff is affiliated with INSERM - the French National
Institute of Health and Medical Research - and the University of
Paris 11.

Researchers suspected that moles, also known as nevi, and
breast cancer might share links to certain hormones and genes.
That would mean moles could be used to help predict a woman's
breast cancer risk.

"We always need to discover more causes of cancer and breast
cancer in particular," Kvaskoff said. "If more studies were to
find nevi were associated with breast cancer risk, then nevi
could become a risk marker for breast cancer risk."

In one of the studies, researchers led by Mingfeng Zhang at
Brigham and Women's Hospital in Boston used data collected on
74,523 female nurses between 1986 and 2010 to measure women's
breast cancer risk by the number of moles on their arms.

Women with no moles had about an 8.5 percent chance of
developing breast cancer during the study, compared to an 11.4
percent chance of breast cancer among women with 15 or more
moles on their left arm.

Among women who had already gone through menopause, Zhang
and her colleagues found those with six or more moles had higher
levels of estrogen and testosterone in their blood, compared to
women without moles.

After adjusting their data to account for the differing
hormone levels, the researchers found the link between moles and
breast cancer disappeared.

In the other study that was led by Kvaskoff, researchers
found that French women who reported having "very many moles"
were 13 percent more likely to develop breast cancer between
1990 and 2008 than women who had no moles. That study included
89,902 total women.

The association disappeared after the researchers adjusted
the data to account for other breast cancer risk factors,
including family history of breast cancer.

Kvaskoff said the findings suggest that the link between the
number of moles a woman has and her risk of breast cancer could
be genetic or hormonal. Her team did not have the data to take
hormones into account, however.

The new studies, published in PLOS Medicine, are also
limited because they mostly relied on white women. Additionally,
one study asked women to report their own moles, which may be
unreliable.

Kvaskoff said the magnitude of the associations the
researchers found was small, which suggests moles may not be an
important risk factor.

In an editorial accompanying the new studies, Barbara
Fuhrman and Victor Cardenas from the University of Arkansas in
Little Rock write that more research is needed.

They say that they hope additional studies will add
information on the relationship between moles and breast cancer,
and help with the assessment of breast cancer risk.

For now, Kvaskoff said the biggest risk of moles is skin
cancer.

"Women in general should always get their moles checked for
this reason," she said. "But it shouldn't be a concern with
breast cancer."